I. Field of the Invention
The present invention relates to a surface porous film. More particularly, the present invention relates to a surface porous film which is suitable as a film for printing such as offset printing and for ink-jet recording, and suitable as an anti-fog film, etc.
II. Description of the Related Art
Since plastic films have poor water or oil absorption, when they are used as a film for offset printing or ink-jet recording, a porous layer for absorbing the ink or the solvent in the ink is formed on the surface of the plastic film.
The conventional films are well-known in the art, which have a porous surface layer containing large particles of an inorganic filler such as talc, calcium carbonate, kaolin or clay, or organic powder such as plastic pigment, in which surface layer the porosity is assured by the clearance among the particles (Japanese Patent Publication No. 22997/88).
However, in such conventional films, since the porosity is provided by the clearance among the particles, the pores are connected one another and the pore size is not uniform. Therefore, the ink is likely to flow in the lateral direction so as to cause blotting of the ink or to show non-uniform ink absorption. Further, since a large amount of large inorganic particles are contained, the smoothness of the surface of the film is low and non-printed spots in the form of pin holes and irregularity of the printing are likely to generate due to the dropping off of the particles. Further, since the strength of the coated layer is small, dust is likely to generate when the films are cut.